1. Field of the Invention
This invention relates to a trim and/or tilt mechanism for a marine outboard drive and more particularly to an improved trim and/or tilt mechanism that includes a hydraulic cylinder device disposed transversely offset from the center axis of the mechanism per se.
2. Description of Related Art
As an example of the marine outboard drive, generally an outboard motor has a drive unit mounted on an associated watercraft by means of a trim and/or tilt mechanism which comprises a swivel bracket and a clamping bracket. The swivel bracket carries the outboard drive unit for pivotal movement about a generally vertically extending steering axis. The clamping bracket, in turn, is affixed to the transom of an associated watercraft with a pair of horizontally spaced members and supports the swivel bracket for pivotal movement about a generally horizontally extending tilt axis.
The trim and/or tilt mechanism includes also a hydraulic cylinder assembly disposed between the swivel bracket and the clamping bracket so that the swivel bracket as well as the drive unit is tilted up or down relative to the clamping bracket and eventually to the transom of the associated watercraft. The fluid motor is, for example, a compound trim and tilt hydraulic cylinder device. An exemplary hydraulic cylinder device is shown in the U.S. Pat. No. 5,718,613.
The hydraulic cylinder device includes an outer cylinder housing, a tilt cylinder slidably supported in the outer cylinder housing, a tilt piston slidably supported in the tilt cylinder and a piston rod affixed to the tilt piston at its one end and extending outwardly from both of the tilt cylinder and the outer cylinder housing. The other end of the piston rod is pivotally connected to the swivel bracket, while the outer cylinder housing is also pivotally connected to the clamping bracket. Hydraulic fluid is contained in the cavities formed in the cylinder housing and also the tilt cylinder and pressurized selectively by a powering assembly to move the piston rod either one of the expanding direction or contracting direction.
By this selective movement of the piston rod, the drive unit can be lifted up or lowered down. If an operator of the outboard motor wishes to adjust the trim angle of the drive unit, the operator operates the hydraulic cylinder device within a trim range. During this trim range operation, the tilt cylinder acts as a trim piston and moves relatively slow but produces large force. Meanwhile, if the operator wishes to tilt up or down the drive unit, he or she operates the hydraulic cylinder device within a tilt range. In this range, the tilt piston moves and this time relatively quick but produces small force.
As described above, the mechanism will operate as a trim and tilt mechanism with this hydraulic cylinder device. Some mechanism, however, is provided with either a trim cylinder device or a tilt cylinder device. Thus, the term "tilt mechanism" will mean not only the tilt mechanism per se but also the trim and tilt mechanism and even a single trim mechanism in the broad sense hereunder wholly through this specification including claims unless depicted otherwise.
The powering assembly comprises a reversible electric motor, a reversible hydraulic pump driven by the electric motor and a fluid reservoir. In order to minimize the size of the tilt mechanism, usually the powering assembly is placed between the spaced members of the clamping bracket side by side with the hydraulic cylinder device. Since the place for the hydraulic cylinder device and the powering assembly is not so spacious, it means that the hydraulic cylinder device must be decentered transversely from the axis of the tilt mechanism. This arrangement gives rise to a problem.
That is, the lifting or lowering force exerted onto the piston rod and the outer cylinder housing affects the swivel bracket and the clamping bracket as an offset load and this offset load is likely to deform the bracket assembly. If the brackets have sufficient thickness entirely, rigidity will be enough. However, this resolution apparently increases the whole weight of the bracket assembly.
It is, therefore, a principal object of this invention to provide an improved tilt mechanism to solve the problem.
It is another object of this invention to provide a tilt mechanism that will hardly cause such a deformation in its bracket assembly without having futile weight.